1. Field of the Invention
The present invention relates to an electronic component-embedded module which includes an electronic component provided in a flexible multilayer board and is adapted to be mountable on a motherboard.
2. Description of Related Art
An example of a conventional electronic component-embedded module of this type is a component-embedded wiring board (simply referred to below as a wiring board) described in Japanese Patent Laid-Open Publication No. 2009-260318. This wiring board includes a core substrate having an approximately rectangular shape. The principal surface of the core substrate (referred to below as the principal surface of the core) has a principal-side built-up layer provided thereon, and the opposite surface to the principal surface (referred to below as the opposite surface of the core) has a bottom-side built-up layer provided thereon.
The core substrate has an accommodating hole (i.e., a cavity), which is a rectangular through-hole when viewed in a top view. In the accommodating hole, an IC chip (semiconductor integrated circuit element), which is an example of the electronic component, is placed. Note that the gap between the accommodating hole and the IC chip is filled with a resin filler, so that the IC chip is fixed to the core substrate.
The principal-side built-up layer has a structure in which three principal-side resin interlayers made of thermosetting resin and principal-side conductor layers made of copper are laminated alternatingly. Moreover, the principal-side resin interlayers include first via-conductors made by copper-plating. Some of the first via-conductors are connected to the IC chip.
Another example of the electronic component-embedded module is an Si-based package described in Japanese Patent Laid-Open Publication No. 2008-42904. This Si-based package includes an interposer (i.e., a multilayer board) provided in its lower part and having an etched cavity for an RFIC chip, which is another example of the electronic component. The cavity is metal coated to facilitate shielding. Moreover, the RFIC chip is flip-chip bonded to an added portion of the Si-based package using microbumps.
The electronic component-embedded module is mounted on a motherboard. However, the multilayer board and the motherboard are made from materials having different coefficients of thermal expansion from each other. Accordingly, if the motherboard is deformed (typically, warped), bonding portions of the electronic component and the multilayer board might be broken as a result of stress being applied thereto.
Particularly in recent years, the bonding portions of the electronic component and the multilayer board have been becoming smaller as the electronic component-embedded module comes to have a more compact size and a further advanced functionality. As the bonding portions become smaller in such a manner, the possibility of the bonding portions being broken even by small stress increases.